I got a Raspberry Pi 3 B+ with 2.5A power supply that came with it. I've connected a VGA monitor (via an HDMI-VGA adapter) and keyboard to it, and connected it to the WiFi.
From the beginning, the screen has been going blank erratically. Usually for short but frequent periods. I thought it was the HDMI-VGA adapter or the VGA cable, but I've connected them to my laptop and its experiencing no issues.
I've just noticed right now, that the times the screen goes blank correspond with WiFi activity. If I install packages, the screen will go blank while the download is in progress. If I ping from the RPi, it will go blank until I kill ping with Ctrl-C. If I connect via ssh to it, the screen will go blank while I'm typing from the remote ssh client or the server is responding. I've disconnected the WiFi, and connected the RPi by ethernet, and the issue is gone...
I'm using Arch Linux ARM with no X server (just the linux consoles (e.g. tty1)).
Is this an issue with lack of power? Or is the wifi interfering with the adapter's electronics due to lack of EM shielding or something?